Intraoperative Microelectrode Recording

Abstract

Deep brain stimulation (DBS) is widely used and is effective for treating involuntary movement disorders or intractable pain. DBS electrodes are typically implanted in deep brain structures such as the subthalamic nucleus and pallidum, which form part of the cortex–basal ganglia loop. These target structures are small and are surrounded by other vital neural structures. Therefore, the outcomes depend on whether the electrodes can be implanted accurately. Prior to surgery, patients are fitted with a stereotactic apparatus, and the target site is anatomically identified by imaging with the apparatus in place. Advances in planning software and other MRI guidance technologies now enable safer and more accurate surgery. Nevertheless, clear visualization of target sites on images remains difficult, and inaccuracies may result from imaging distortions due to the MRI magnetic field, errors caused by the stereotactic apparatus frame, other aspects of the system itself, and brain movement due to intraoperative cerebrospinal fluid leakage. Microelectrode recording (MER) of extracellular activity is used to identify and confirm targeted sites that are provisionally identified by imaging. The optimum sites for microelectrode placement are determined by intraoperative test stimulation to observe the stimulus-evoked effects. The objective of intraoperative MER for DBS is to use the characteristics and patterns of extracellular neural activity to identify the relative location of the target site (mapping). Here, we focus on MER during DBS surgery and intraoperative trial stimulation.